Wide Format Officejet 7000 Paper Mismatch

I've done all the formatting in my applications (mostly in Word) and yet my Officejet 7000 will not print on my 8.75 x 5.75 envelopes. I'm trying to find a way to set a custom page size in the print driver. I have confirmed the settings in Word are correct, but the driver is - for some stupid reason - looking for 8.5 x 11 paper. Any help would be greatly appreciated.

C'mon, HP. Let's go back to making printers that would print on whatever size paper you put in them!